Current stabilizer having a saturable reactor in the mode of forced magnetization

ABSTRACT

A current stabilizer having a saturable reactor in the mode of forced magnetization is adapted to control and stabilize both direct and alternating currents in the load, the wave form of the alternating current in the load being rectangular. The current stabilizer comprises working windings of the saturable reactor being separated into voltage working windings and current working windings which are switched over by power-controlled rectifiers when passing from the excitation mode into the conductivity mode, thus reducing the overall dimensions and weights of the current stabilizer.

United States Patent Lepp et al.

[451 Oct. 29, 1974 l l CURRENT STABILIZER HAVING A SATURABLE REACTOR IN THE MODE OF FORCED MAGNETIZATION 176] inventors: Vladimir Romanovich Lepp, ulitsa Govorova 3, kv. 83; Kharis Malikovich Sihgatulin, Beskudnikovsky bulvar 32, korpus 4, kv. 56; Jury Nikolaevich Cherkasov, proezd Cherskogo 9, kv. 35, all of Moscow, USSR.

22 Filed: Apr. 11,1973

121] Appl. No.: 350,138

[301 Foreign Application Priority Data May 22, 1972 U,S,S.R 1786614 [52] U.S. Cl 323/7, 321/25, 323/24, 323/39 [51] Int. Cl. H02m 5/28, H02m 7/20 1581 Field of Search 321/16, 18, 25; 323/4, 323/7. 24, 39

[56] References Cited UNITED STATES PATENTS 3,018,383 1/1962 Ellert 323/24 UX 3,129,381 4/1964 Manteuffel 323/24 3,295,054 12/1966 Gutzwiller et a1 3,454,862 7/1969 Kurimura et a1 321/18 Primary Examiner-A. D. Pellinen Attorney, Agent, or FirmHolman & Stern 5 7] ABSTRACT 4 Claims, 10 Drawing Figures ALTERNAT/NG VOLTAGE SOURCE LOAD D/REC 7' VOL TA GE SOURCE CURRENT STABILIZER HAVING A SATURABLE REACTOR IN THE MODE OF FORCED MAGNETIZATION BACKGROUND OF THE INVENTION The present invention relates generally to controlled load current stabilizers and more specifically. it relates to one of the varieties of parameter stablizers, saturable reactors, operating under forced magnetization conditrons.

This type of saturable reactor may be applied in any field of engineering and technology which calls for a constant value of the load current and the adjustment thereof within a wide range. Specifically, it may be used both in a.c. and do. arc welding, constricted are cutting, electric arc remelting, electrolysis. electroplating, electrochemical processing, transmission of electric energy with a constant load in the transmission line, etc.

In the prior art, there is an unbiased saturable reactor comprising control windings and an ac. winding made up by two sections differing in number of turns, which are commutated by high-speed controlled rectifiers, while the section having more turns is connected to the load circuit within an excitation interval, and the section having fewer turns is connected to that circuit within a conduction interval.

This prior-art saturable reactor suffers from the following disadvantages: the ripple factor of the load current varies within a wide range, both with a change in the resistance of the load or the voltage of the power line and during an adjustment of the load current the mean value ofthe current remaining unchanged); while being connected to a rectifier bridge with an inductancc filter and a load in the dc. circuit, the operation of the saturable reactor brings about disturbances in the stabilization of the load current; such disturbances in the load or the power line may result in temporary deviations in the means value of the load current.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a saturable reactor operating under forced magnetization conditions. the waveform of the load current thereof being rectangular, thus stabilizing the instantaneous, mean and effective values of the load current. and which also eliminates a current transient caused by disturbances both in the power line and the load (with definite values of disturbances).

With this aim in view, the present invention resides in that a saturable reactor comprising control windings, separated working current and potential windings and a tap-changer made up by controlled rectifiers and shunting the control windings within a conduction interval, is provided. according to the invention, with a line choking coil connected in series with the circuit of the control winding, while an additional line choking coil is connected in series with the load circuit, the working potential windings being connected via a diode between the anode and control electrode of the controlled rectifiers.

When the saturable reactor is used with the sole purpose of stabilizing an alternating current value, it is expedient that it use a differential circuit, i.e., the winding of the line choking coil in the load circuit be provided with a tap in the middle thereof connected in series with the current winding of the saturable reactor, the winding itself being connected between the anode and cathode of the controlled rectifiers.

When the saturable reactor is used to stabilize both a direct and a monophase alternating current value, it is expedient that the controlled rectifiers be connected in a monophase bridge circuit, while the line choking coil is connected to the dc. circuit of the bridge.

In order to stabilize a direct and a polyphase alternating current value, the controlled rectifiers are connected in a polyphase bridge circuit. the line choking coil in the load circuit is connected to the dc. circuit of the bridge, the number of the working potential windings in the anode-control electrode circuit corresponds to the number of phases, the windings are connected in series aiding, while each core of the saturable reactor is wound with working potential windings connected to the cooperating arms of the bridge, the number of these windings also corresponding to that the phases.

The saturable reactor disclosed herein makes it possible to provide universal, with respect to the type of current, controlled current stabilizers of practically unlimited power rating, having excellent characteristics in terms of volume, weight and values of current and voltage amplification factors (10 and 10, respectively), also having a good linear control e aracteristic and marked by the absence of a current transient due to disturbances in the load or the power line, and by the parametric action of stabilization.

The simplicity of the circuitry of this saturable reactor ensures high reliability and facility in servicing, makes unnecessary any adjustment and alignment, and retains high quality of regulation and stabilization of both direct and alternating currents of rectangular waveforms.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in greater detail with reference to embodiments thereof in conjunction with the accompanying drawings, wherein:

FIG. 1 is a circuit diagram of a saturable reactor using a differential circuit with separated working windings, in accordance with the invention;

FIG. 2 is a circuit diagram of a saturable reactor using a monophase bridge circuit, in accordance with the invention;

FIG. 3 is a circuit diagram of a saturable reactor using a three-phase bridge circuit, in accordance with the invention;

FIG. 4 is a graph representing waveforms of the supply voltage;

FIG. 5 is a graph representing time-variable waveforms of the load current;

FIG. 6 is a graph representing time-variable wavefonns of the voltage across the windings of the line choking coil in the load and control circuits;

FIG. 7 is a graph representing waveforms of the voltage across one of the windings of the saturable reactor;

FIG. 8 is a graph representing waveforms of the volt age across the other winding of the saturable reactor;

FIG. 9 is a graph representing waveforms of the current through the control electrode of one of the rectifiers; and

FIG. 10 is a graph representing waveforms of the current through the control electrode of the other rectifier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The saturable reactor with separated working windings shown in FIG. 1, uses a differential circuit and comprises an alternating voltage source I, a tapchanger made up by controlled rectifiers 2 and 3, diodes 4 and 5 connected to the anode-control electrode circuit of the controlled rectifiers 2 and 3 via working potential windings 6 and 7 of the saturable reactor, which are wound on cores 8 and 9, respectively.

The central tap of the winding of the line choking coil made up by series-connected sections 10 and H (the points indicate the starts of the windings) is connected to the circuit of current working windings l2 and 13 of the saturable reactor connected in series opposition and of a load 14.

Control windings l5 and 16 of the saturable reactor, which are connected in series aiding, are placed in series with a winding I7 of-an additional line choking coil and to a direct voltage source 18.

The saturable reactor shown in FIG. 2 uses a monophase bridge circuit and comprises an alternating voltage source 19, controlled rectifiers 20, 21, 22 and 23 forming a tap-changer which serves as a bridge rectifier, connected to the direct current circuit whereof is a line choking coil 24. The anode and control electrode of each controlled rectifier are interconnected via working potential windings 25, 26, 27 and 28 of the saturable reactor and diodes 29, 30, 3| and 32, the working potential windings 26 and 27 being wound on a core 33, and the windings 25 and 28, on a core 34. Working current windings and 36 of the saturable reactor, also wound on the cores 33 and 34, respectively, are inter-connected in series opposition in a load circuit 37. A circuit consisting of a winding 38 of an additional line choking coil and control windings 39 and 40 of the saturable reactor, connected in series aiding, is connecled to a direct voltage source 41.

FIG. 3 is a diagram of a three-phase saturable reactor with separated working windings. The saturable reactor comprises a three-phase power source 42 whose voltage is supplied, via working current windings 43, 44, 45, 46, 47 and 48 of the three-phase saturable reactor wound on cores 49, 50, 51, 52, 53 and 54, respectively, to a three-phase rectifier bridge made up by controlled rectifiers 55, 56, 57, 58, 59 and 60 which form a tapchanger.

Control windings 6|, 62, 63, 64, and 66 of the saturable reactor are connected in series aiding, while a winding 68 of a line choking coil is connected to the circuit of the control windings 6|, 62, 63, 64, 65 and 66 and a direct voltage source 67.

Connected to the anode-control electrode circuit of the controlled rectifiers 55-60 via diodes 87, 88, 90, 9| and 92 are working windings 69, 70, 7|, 72, 73, 74, 75, 76, 77, 78, 79, 80, 8|, 82, 83, 84, and 86 of the saturable reactor.

Connected in series aiding with the anode control electrode circuit are three working potential windings, 69, 70, 71 of 72, 73, 74, etc.. of the saturable reactor, which are wound on different cores. The order of their connection is determined by that of the connection of the current working winding, while their number is equal to that of the phases. This embodiment of the saturable reactor renders it insensitive to changes in the order of phase alternation when the saturable reactor is connected to the power line.

Connected in series with the circuit of the threephase bridge are a winding 93 of a line choking coil and a load 94.

The saturable'reactors shown in FIGS. 2 and 3 make it possible to stabilize both the direct current through the load and alternating current. For this purpose, the load is connected either to the dc. circuit of the rectifier bridge or to its power supply circuit.

The saturable reactor operates as follows.

First, the connection of the direct voltage source 18 (FIG. I) to the circuit of the control windings l5 and 16 of the saturable reactor via the winding [7 of the additional line choking coil sets a predetermined value of the control current through the circuit. The cores 8 and 9 of the saturable reactor are saturated.

The voltage applied from the source 7 energizes the rectifiers 3 and 2 at the beginning of each alternation of circuits 95 and 96 (FIG. 4).

The load current which flows through the circuit: source I (FIG. 1), rectifier 2 (or 3), winding |0 (II), current working windings l2 and I3, load 14, increases from zero to a definite value equal to I l istisil izuail' m where I is the load current, I, is the control current through the circuit of the windings l5 and 16, W and W each stand for the number of turns of the respective windings.

The factor which accounts for a gradual increase in the load current is the line choking coil with the winding |0-l l. The current increasing, the line choking coil stores a growing amount of magnetic energy which ultimately reaches a value equal to m td-ll nn i where W, is the magnetic energy of the line choking coil, L is the inductance value.

Within a time interval when the amount of the magnetic energy, stored in the line choking coil increases there is no recuperation of reactive energy in the circuit.

Further on, the saturable reactor maintains the value of the magnetic energy stored by the line choking coil at a stable level due to a parametric phase adjustment by that value of the energy supplied from and to the power line, thus maintaining the current through the load circuit constant and at level preset by the control circuit.

During a time interval 1, 1,, (FIG. 4), the rectifier 3 is conducting with respect to the core 9 (FIG. 1), the core 9 is saturated and shunts the working potential winding 7, the control current from the source 18 passes through the winding 17 of the additional line choking coil and the control windings l5 and 16, the load current 97 (FIG. 5) passes from the alternating voltage source 1 via the rectifier 3, the winding ll of the line choking coil, the current working windings l2 and 13 of the saturable reactor and the load 14. The magnetic charge of the core 8 of the saturable reactor reverses in sense, and a voltage 105 (FIG. 8) is induced in the winding 6, which is equal and opposite to a voltage 100 across the line choking coil (FIG. 6).

At time the core 8 reaches saturation, the voltage 103 (FIG. 7) is equal to zero, the voltage 100 (FIG. 6)

across the winding -11 originates a current 106 (FIG. 9) through the winding 6, diode 4 and the control electrode of the rectifier 2 (FIG. I); the rectifier 2 is energized, the voltage 95 of the power line (FIG. 4) is at the moment rectified therefor and the rectifier 3 (FIG. 1) is de-energized and shunts the working potential winding 6. The load 14 is traversed by the current 98 of reverse polarity (FIG. 5). The core 8 remains saturated, the magnetic charge of the core 9 reverses in sense, being shifted by the control ampere-turns of a constant value. A voltage 101 is induced in the line choking coil with the windings 10-11 (FIG. 6), which is equal to a difference of instantaneous values of the voltage 95 of the power line and the load current 98 (FIG. 5) multiplied by the resistance value of the load 14. A voltage 105 (FIG. 8) is induced in the winding 7, which is equal and opposite to the voltage 101 (FIG. 6) of the line choking coil.

At time the voltage of the circuit reverses in polarity, due to the energy stored in the line choking coil with the winding 10-11; the load current 98 retains its direction. and the rectifier 2 remains energized. Integration of the reactive flux continues in the core 9.

At time l the integration is over, the core 9 (FIG. 1) is saturated, the winding 7 and diode 5 are traversed by a current 107 (FIG. 10) which energizes the rectifier 3; the load 14 is traversed by the current 99 (FIG. 5); the voltage 102 (FIG. 6) is induced in the line choking coils with the windings 10-11 and 17; the magnetic charge of the core 8 reverses in sense; beginning with time the entire sequence of events just described is repeated all over again.

The circuit shown in FIG. 2 operates in a similar manner, differing only in that the elements for switching the additional line choking coil are connected in a bridge circuit, instead of the differential circuit shown and disclosed in FIG. 1.

Within the interval of time t -r (FIG. 4) which is a conductivity interval for a core 33 (FIG. 2) the core 33 is saturated. the rectifiers 21 and 22 conduct and shunt the voltage working windings 26 and 27. The control current from the source 41 flows along the winding 38 of the additional line choking coil, the control windings 39 and 40 and the load current 97 (FIG. 5) flows from the source 19 of ac voltage through the rectifier 21, the winding 24 ofthe line choking coil, the rectifier 22, the current working windings 35 and 36 of the saturable reactor and the load 37. The core 34 of the saturable reactor is re-magnetized, produced on the windings 25 and 28 is the voltage 103 (FIG. 7) equal and opposite to the voltage 100 (FIG. 6) on the winding 24 of the line choking coil.

At the moment of time I. the core 34 is saturated. the voltage 103 (FIG. 7) is equal to zero, the voltage 100 (FIG. 6) on the winding 24 of the line choking coil produces the current 106 (FIG. 9) in the windings 25 and 28 and control electrodes of the rectifiers and 23 (FIG. 2) the rectifiers 20 and 23 are cut in since the voltage 95 ofthe mains (FIG. 4) at this moment of time is applied thereto in the direct polarity. The rectifiers 20 and 23 shunt the voltage working windings and 28, respectively.

The rectifiers 2] and 22 (FIG. 2) are cut off since the mains voltage 95 at this moment of time is applied thereto in the inversed polarity.

The current 98 in the load changes its sense (FIG. 5). The core 34 remains saturated. meanwhile the core 33 is re-magnetized by the control current. Produced on the winding 24 of the line choking coil is the voltage 101 (FIG. 6) equal to the difference of the instantaneous values of the mains voltage and the load voltage equal to the load current 98 (FIG. 5) multiplied by the value of the resistance of the load 37.

At the moment of time t the mains voltage changes its sense. the load current 98 keeps its direction due to the energy accumulated in the winding 24 of the line choking coil, and the rectifiers 20 and 23 remain cut-in. The core 33 continues integrating the reactive stream.

At the moment of time t the core 33 (FIG. 2) is saturated, the current 107 (FIG. 10) flows along the windlugs 26 and 27 and cuts off the rectifiers 21 and 22, the current 99 (FIG. 5) flows in the load 37, the voltage 102 (FIG. 6) is produced on the windings of the choking coils 24 and 38, the core 33 (FIG. 2) remains saturated. the core 34 is remagnetized and the process is repeated again beginning from the moment of time 1,.

The circuit shown in FIG. 3 does not differ by its physical processes in its elements from the circuit shown in FIG. 2. The multi-phase power source 42 determines the general increase in the number of the cores in the saturable reactor as well as the increase in the number of voltage working windings introduced into the circuit anode-control electrode of the rectifiers.

The number of voltage working windings connected to the anode-control electrode circuit of the control rectifiers correspond to the number of phases, the number of voltage working windings being disposed on each of the cores also corresponding to the number of phases.

The circuit (FIG. 3) operates as follows:

From the direct current voltage 67, the bias current is fed to control windings 61-66 of the saturable reactor. All of the cores 49-54 are saturated, the control signals are fed from the anodes of the rectitiers 55-60 being controlled and the circuit operates as a known diode bridge.

The load current increases and at the moment when it obtains the required value, the current stabilizer begins operating in the mode of stabilization. The further increase of the load current causes the condition when the cores of the current conducting phase wherein the magnetic streams produced by the load current and control current are in series opposite are put out of the saturation and the voltage working windings of these cores produce a voltage equal and opposite to the voltage produced at the output of the multiphase bridge.

One of the voltage working windings is in the control circuit of the controlled rectifier which according to the order of phase alternation should be subsequent. However, when the supply voltage polarity is current conducting for the controlled rectifier, the voltage on the voltage working windings and on the winding 93 of the line choking coil changes synchronously the sense and hence the current is not present in the circuit of the control electrode of the controlled rectifier and therefore the controlled rectifier is not cut-in. However, due to the energy stored in the line choking coil in the load current cannot change instantaneously and the current of the same sense will continue flowing along the load. This will continue until the line choking coil 93 returns to the mains the excess of the energy, stored above the required value determined by the bias current. Hence, the core connected to the circuit anode-control electrode of the controlled rectifier is saturated and the controlled rectifier is cut-in.

Assuming that the phase of the supply voltage of the controlled rectifiers 56 and 57 are cut-in. ln that event, the cores 49 and 52 are saturated meanwhile the cores 50 and 51 are remagnetized. When the next phase of the supply voltage is present the controlled rectifiers 56 and 59 are cut-in. The controlled rectifier 56 remains cut-in from the previous phase, but the controlled rectifier 59 cannot be cut-in since although the cores 49 and 54 are saturated, the core is remagnetized and the load current continues flowing along the circuit of the controlled rectifiers 56 and 57 through the load 94 due to the energy accumulated in the line wchoking coil 93. After being saturated, the core 51 the controlled rectifier 59 is cut-in and the current flows along the circuit of the controlled rectifiers 56 and 57 and through the load 94 whereas the line choking coil 93 stores the energy. The voltage working windings 76 and 77 of the cores 49 and 54 are connected to the circuit of the control electrode of the controlled rectifier 59 to make possible the condition that the-current stabilizer will be insensitive to the order of phase alternation.

What is claimed is:

1. A current stabilizer having saturable reactor in the mode of forced magnetization, said current stabilizer comprising in combination:

an AC voltage source;

a DC voltage source;

a load;

a saturable reactor being formed by cores having voltage working windings, current working windings, and control windings disposed thereon, said control windings being connected in series to each other and separated by said voltage working windings and said current working windings, said saturable reactor being connected in series between said AC voltage source and said load; tap-changer being formed by controlled rectifiers, said rectifier having an anode, a cathode and a control-electrode, said AC voltage source being connected in series between said tap-changer and said load;

diodes being connected in series in said voltage working windings of said saturable reactor, said diodes and said voltage working windings being connected between said anode and said control electrode of said rectifier;

a first line choking coil having a winding connected in series between said rectifiers of said tap-changer and said current working windings, said current working windings being connected in series to said load; and

a second line choking coil being connected in series to said control windings, said second line choking coil and said control windings being connected in parallel to said DC voltage source.

2. A current stabilizer as claimed in claim 1, wherein said controlled rectifiers of said tap-changer is a differential circuit, said windings of said first'line choking coil being connected at one end thereof to said anode of one of said controlled rectifier, the other end of said windings being connected to said cathode of another one of said controlled rectifier, said winding of said first-line choking coil having a central tap connected in series to said current working winding.

3. A current-stabilizer as claimed in claim 1, wherein said controlled rectifiers of said tap-changer are connected to form a single-phase bridge circuit, said first line choking coil being connected to the dc. circuit of said bridge circuit.

4. A current stabilizer as claimed in claim I, wherein said controlled rectifiers of said tap-changer are connected to form a multi-phase bridge circuit, said first line choking coil being connected to the dc. circuit of said bridge circuit, said voltage working windings being connected in series aiding, the number of said voltage working windings being equal to the number of phases, the number of said voltage working windings disposed on each of said cores of said saturabie reactor which are connected to the operating arms of said bridge being also equal to the number of phases. 

1. A current stabilizer having saturable reactor in the mode of forced magnetization, said current stabilizer comprising in combination: an AC voltage source; a DC voltage source; a load; a saturable reactor being formed by cores having voltage working windings, current working windings, and control windings disposed thereon, said control windings being connected in series to each other and separated by said voltage working windings and said current working windings, said saturable reactor being connected in series between said AC voltage source and said load; a tap-changer being formed by controlled rectifiers, said rectifier having an anode, a cathode and a control-electrode, said AC voltage source being connected in series between said tap-changer and said load; diodes being connected in series in said voltage working windings of said saturable reactor, said diodes and said voltage working windings being connected between said anode and said control electrode of said rectifier; a first line choking coil having a winding connected in series between said rectifiers of said tap-changer and said current working windings, said current working windings being connected in series to Said load; and a second line choking coil being connected in series to said control windings, said second line choking coil and said control windings being connected in parallel to said DC voltage source.
 2. A current stabilizer as claimed in claim 1, wherein said controlled rectifiers of said tap-changer is a differential circuit, said windings of said first-line choking coil being connected at one end thereof to said anode of one of said controlled rectifier, the other end of said windings being connected to said cathode of another one of said controlled rectifier, said winding of said first-line choking coil having a central tap connected in series to said current working winding.
 3. A current-stabilizer as claimed in claim 1, wherein said controlled rectifiers of said tap-changer are connected to form a single-phase bridge circuit, said first line choking coil being connected to the d.c. circuit of said bridge circuit.
 4. A current stabilizer as claimed in claim 1, wherein said controlled rectifiers of said tap-changer are connected to form a multi-phase bridge circuit, said first line choking coil being connected to the d.c. circuit of said bridge circuit, said voltage working windings being connected in series aiding, the number of said voltage working windings being equal to the number of phases, the number of said voltage working windings disposed on each of said cores of said saturable reactor which are connected to the operating arms of said bridge being also equal to the number of phases. 